Separating wax from oil



June 25, 1935. H, v. ATWELL SEPARATING WAX FROM OIL Filed Oct. 26, 1931 m w .A Mi i H mm M m in e M a. Z a w u w v 0 -12 M M 3 ow Z L W N 1 H v0. Z W nw v L w M W m WW m n a Patented June 25, 1935 I UNITED STATES PATENTOFFICE SEPARATING WAX FROM OIL Harold V. Atwell, Hammond, Ind., asslgnor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application October 26, 1931, Serial No. 571,150

4 Claims. (Cl. 196-19) This invention relates to a process for separate a n ng un a in Composition after ihg Wax from s and it pertains more particustillation due .to the similarity in boiling points of larly to the dewaxing of viscous petroleum lubrithe possible c p h invention will be eating oils to obtain the desired low pour point o e a y understood from the following 5 characteristics. tailed description of a preferred embodiment. 5

In the manufacture of petroleum lubricating In t accompanying drawing, w ch fo ms 3 oils it is necessary to remove substantially all of pa t of t Specification, I have dia ra at the wax in order that the oil may flow freely at Ca shown on elevatiohel p of my p ved low temperatures. This is usually accomplished systemby diluting a viscous wax-bearing oil with a light The diluent storage tank '0 is Preferably d 10 diluent, such as naphtha, chilling the mixture to signed to Withstand pressures of several hundred about to 40 F. to separate out the wax, pounds and it may be insulated and provided with and mechanically separating the wax from the means ool the ent w ic is stored diluted oil. In order to obtain an oil of the very therein. h diluent, pr f ethyl chloride 5 lowest pour test consistent with its viscosity, it in this p y be xed u may even be necessary to chill to 60 F. The With a light hydrocarbon mixture of pp ease with which the wax may be separated from mately the same boiling p in h as pr p n the oil depends on the form in which the wax In place of methyl chloride I may similarly use crystallizes, the solubility of the wax in the dilutethyl id o-d fluo e hane or 20 ed oil, the viscosity and specific gravity of the dione of h other compounds previously entioned. 2 luted oil, etc. under the temperature and pressure Higher boiling halogenated hy arbons are unconditions of the dewaxing apparatus The 1 satisfactory because of the difliculty of attaining ject of my invention is to provide a diluent which the low temperature neeessary'fol refrigerating will give oil mixtures of extremely low viscosity and completely deWaXihg the il.

35 and low specific gravity, which will dissolve sub- The liquefied diluent is conducted from Storage 25 stantially no wax and which will bring about tank u h pip H in am u s r ulat d by the crystallization of the wax in such a manner Valve into mixer wherein it is mixed W t that it can be easily separated from the diluted the Viscous WaX-heerihgiuhrioating Oil introduced oil. A further object is to provide a system for by p pe The Wax-hearing oil may he of any refrigerating the oil conveniently and economiyp t in y Preferred b d t I ave de- 30 cally and in such a manner that the crystallized scrib a treated, Wax hearing, overhead lubricatwax will be readily filterable from the oil. ing out hav a Viscosity of about 1500 e d I have discovered that certain chlorine and Sayholt at fiuorine derivatives of light hydrocarbons are re- The mixture of oil and diluent is introduced by a markably effective as antisolvents and diluents pipe [5 into chill chamber I6 which may be a u for the separation of wax from oil. In order to large insulated drum. Instead of introducing all obtain the low temperatures necessary I require of the diluent with the oil I may bypass some or halogenated solvents with boiling points lying all of said diluent through pipe l'l, valve l8, heat below 20 C. The following chlorine and fluorexchanger l9 and pipe 20 into the base of said 0 inc compounds are examples of such solvents chamber. By this expedientIam enabled to chill m which I may employ: methyl chloride, methyl the diluent in the absence of wax so that there fluoride, ethyl fluoride, difluoro-methane, trifiuwill be no accumulations of wax in the exchanger, oro-methane, chloro-fiuoro-methane, dichlorothe chilled diluent being introduced into the body difluoro-methane, monochloro-difluoro-methane, of wax-bearing oil at the base of chill chamber I6.

and monochloro-trifluoro-methane. I prefer to mix about one-third of the diluent 5 These solvents are characterized by their low with the oil in mixer l3, charge the chill chamber viscosity and low solvent power for wax in addiabout one-third full, then discontinue the introtion totheir low boiling points. They can be duction of oil and introduce the remaining twoliquefied by pressure and used as diluents for the thirds of the diluent through pipe l1--2ll.

oil and wax and refrigeration can be obtained by Finally, I have about three to live parts of diluent 50 directly vaporizing a, portion of the diluent from to one part of wax-bearing oil in the chill chamthe solution. I may, if desired, use mixtures of ber. Although the original oil-wax-diluent mixthese diluents with light hydrocarbons, such as ture may have had a temperature of about F., propane, isobutane or mixtures of propane and the temperature of the mixture in the chill chamu butane. Such mixtures have the advantage of her, after complete dilution, may be about 40. F. ll

as a result of cooling the diluent in cooler l9. The temperature reduction is, preferably, gradual (3 to 5 per minute) so that it will result in the formation of relatively large wax crystals. The refrigeration is continued by withdrawing diluent vapors through conduits 2|, and manifold 22, compressing them in compressor 23 and returning them through pipe 24, condenser 25 and pipe 26 to the diluent storage tank III. In this manner I effect self refrigeration of the diluted oil-wax mixture, that is, I abstract heat from the liquid by the vaporization in situ of a portion of said liquid. The cooling from 40 to -l F. may be at a very rapid rate, preferably about 8 to 10 F. per minute. Since the diluent itself has a tendency to throw wax out of solution, satisfactory pour points can be obtained at dewaxing temperatures of 0 to 10 F., the pour point being substantially the same as the dewaxing temperature.

The chilled slurry from chamber I6 is withdrawn by pump 21 through pipe 28 and introduced into the base 29 of filter 30 which is preferably of the vertical type wherein filter leaves 3| are suspended from a removable cover. Filtrate is withdrawn through conduit 32, valve 33 and pipe 34 to accumulation tank or sump 35, from which it may be withdrawn at desired intervals through pipe 36, exchanger l9, pipe 31, exchanger 38 and pipe 29, and introduced into boiler 40 which is heated by steam coils 4|. The wax-free oil is withdrawn from the base of the boiler through pipe 42 and the diluent vapors are withdrawn through pipe 43, exchanger 38, condenser 44 and pipe 45 to diluent storage It]. Vapors from sump 35 and filter 30 are withdrawn through pipes 46 and 41 in amounts regulated by valves 48 and 49; these vapors are compressed in compressor 50 and returned through pipe and condenser 52 to the storage tank Hi.

When a cake has built up on the filter leaves,

' the slurry in the filter press is forced back into the chill chamber and the cake is removed from the leaves and withdrawn from the base of filter 30 through a large valve 54. It is then forced through conduit 55, by means of screw 56 driven by motor 51, into suitable apparatus for recovering diluent vapors and separating the wax from remaining entrained oil, without exposure to the air where loss of valuble diluent vapors may occur. The particular feature of my invention is the use of a wax antisolvent as a refrigerant, the refrigeration being effected by the direct vaporization thereof. This brings about a saving in the cost of refrigeration which is augmented by the fact that the refrigeration need only be carried to about -20 C. to obtain substantially complete dewaxing while heretofore it has been necessary to refrigerate with temperatures as low as 40 C. or even 50 C. The use of higher dewaxing temperatures also increases the rate of filtration and makes it possible to obtain a more complete separation of oil from wax on the filter cake.

While I have described in detail a preferred embodiment of my invention it is understood that I do not limit myself to the details hereinabove set forth except as defined by the following claims. For instance, I may use ordinary filter naphtha, benzene, or other diluents in combination with my volatile antisolvents; in this case some of the antisolvent is used as a refrigerant but it exerts its infiuence on the physical separation of the wax in the chilling step. Other modifications will be apparent to those skilled in the art.

I claim:

1. The process of dewaxing a mineral lubricating oil comprising diluting the oil under pressure with a diluent containing monochloro-difiuoromethane, cooling the diluted oil by reducing pressure and evaporating a portion of the monochlorodifluoro-methane, thus causing the wax to separate from the diluted oil, and subsequently separating the wax from the oil.

2. The method of separating wax from oil which comprises diluting a wax-bearing oil under pressure with a diluent containing a normally gaseous fluoride of a hydrocarbon containing not more than two carbon atoms, said fluoride containing less than two chlorine atoms, cooling the diluted oil to effect solidification of wax, mechanically separating the wax from the diluted oil and removing the diluent from the dewaxed diluted oil.

3. The method of claim 2 wherein the fluoride is methyl fluoride.

4. The method of claim 2 wherein the fluoride is ethyl fluoride.

HAROLD V. ATWEIL. 

